This invention relates generally to an electrophotographic printing device, and more particularly, a lubricating system in the cleaner apparatus that lubricates a detoning roll.
In an electrophotographic application such as xerography, a charge retentive surface (e.g. photoconductor, photoreceptor or imaging surface) is electrostatically charged, and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g. paper), and the image affixed to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is well known, and useful, for light lens copying from an original or printing applications from electronically generated or stored originals such as with a raster output scanner (ROS) where a charge surface may be imagewise discharged in a variety of ways. Ion projection devices, where a charge is imagewise deposited on a charge retentive substrate, operates similarly.
In a reproduction process of the type as described above, it is inevitable that some residual toner will remain on the photoconductor surface after the toner image has been transferred to the sheet of support material (e.g. paper). It has been found that with such a process the forces holding some of the toner particles to the imaging surface are stronger than the transfer force and, therefore, some of the particles remain on the surface after transfer of the toner image. In addition to the residual toner, other particles, such as paper debris (i.e. Kaolin, fibers, clay), additives and plastic, are left behind on the surface after image transfer. (Hereinafter, the term "residual particles" encompasses residual toner and other residual debris remaining after image transfer.) The residual particles adhere firmly to the surface and must be removed prior to the next printing cycle to avoid it's interfering with recording a new latent image thereon.
A commercially successful mode of cleaning employed on automatic xerographic devices utilizes a brush with soft conductive fiber bristles or with insulative soft bristles which have suitable triboelectric characteristics. While the bristles are soft for the insulative brush, they provide sufficient mechanical force to dislodge residual toner particles from the charge retentive surface. In the case of the conductive brush, the brush is usually electrically biased to provide an electrostatic force for toner detachment from the charge retentive surface. Toner particles adhere to the fibers (i.e. bristles) of the brush after the charge retentive surface has been cleaned. The process of removing toner from these types of cleaner brushes can be accomplished in many ways. A common method for providing detoning of these electrostatic brushes is the use of detoning rolls. The particles removed from the brushes adhere to the detoning rolls and are then removed therefrom by scrapers. However, in this method a common problem is that the efficiency of the first detoning roll minimizes toner lubrication to the second detoning roll. This causes cleaning failures due to shorting of the brush bias to the detoning roll. A common compromise is made between performance and life, by slowing down the cleaner to reduce the wear rate and, shortening the scraper blade to reduce end wear of the detoning rolls.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,494,863 to Laing discloses a toner removal device for removing residual toner and debris from a charge retentive surface after transfer of toner images from the surface. This device is characterized by the use of a pair of detoning rolls, one for removing toner from a biased cleaner brush and the other for removing debris such as paper fibers and Kaolin from the brush. The rolls are electrically biased so that one of them attracts toner from the brush while the other one attracts debris.